GRIB学习笔记：样例文件分析 - 概要
目录
本文通过分析一个GRIB2消息介绍GRIB2格式。
样例文件来自中国气象局数值预报中心GRAPES全球模式的预报结果，选用2019年5月26日00时次的000时次850hPa温度场。
GRIB2消息概要
使用grib_dump查看该样例文件包含哪些信息
***** FILE: t.850hpa.000.grb2
#============== MESSAGE 1 ( length=625053 ) ==============
1-4 identifier = GRIB
5-6 reserved = MISSING
7 discipline = 0 [Meteorological products (grib2/tables/4/0.0.table) ]
8 editionNumber = 2
9-16 totalLength = 625053
====================== SECTION_1 ( length=21, padding=0 ) ======================
1-4 section1Length = 21
5 numberOfSection = 1
6-7 centre = 38 [Beijing (RSMC) (grib2/centre.table) ]
8-9 subCentre = 0
10 tablesVersion = 4 [Version implemented on 7 November 2007 (grib2/tables/1.0.table) ]
11 localTablesVersion = 1 [Unknown code table entry (grib2/tables/4/1.1.table) ]
12 significanceOfReferenceTime = 0 [Analysis (grib2/tables/4/1.2.table) ]
13-14 year = 2019
15 month = 5
16 day = 27
17 hour = 0
18 minute = 0
19 second = 0
20 productionStatusOfProcessedData = 0 [Operational products (grib2/tables/4/1.3.table) ]
21 typeOfProcessedData = 0 [Analysis products (grib2/tables/4/1.4.table) ]
====================== SECTION_3 ( length=72, padding=0 ) ======================
1-4 section3Length = 72
5 numberOfSection = 3
6 sourceOfGridDefinition = 0 [Specified in Code table 3.1 (grib2/tables/4/3.0.table) ]
7-10 numberOfDataPoints = 1036800
11 numberOfOctectsForNumberOfPoints = 0
12 interpretationOfNumberOfPoints = 0 [There is no appended list (grib2/tables/4/3.11.table) ]
13-14 gridDefinitionTemplateNumber = 0 [Latitude/longitude (Also called equidistant cylindrical, or Plate Carree) (grib2/tables/4/3.1.table) ]
15 shapeOfTheEarth = 6 [Earth assumed spherical with radius of 6,371,229.0 m (grib2/tables/4/3.2.table) ]
16 scaleFactorOfRadiusOfSphericalEarth = 0
17-20 scaledValueOfRadiusOfSphericalEarth = 0
21 scaleFactorOfEarthMajorAxis = 0
22-25 scaledValueOfEarthMajorAxis = 0
26 scaleFactorOfEarthMinorAxis = 0
27-30 scaledValueOfEarthMinorAxis = 0
31-34 Ni = 1440
35-38 Nj = 720
39-42 basicAngleOfTheInitialProductionDomain = 0
43-46 subdivisionsOfBasicAngle = 0
47-50 latitudeOfFirstGridPoint = 89875000
51-54 longitudeOfFirstGridPoint = 0
55 resolutionAndComponentFlags = 48 [00110000]
56-59 latitudeOfLastGridPoint = -89875000
60-63 longitudeOfLastGridPoint = 359750000
64-67 iDirectionIncrement = 250000
68-71 jDirectionIncrement = 250000
72 scanningMode = 0 [00000000]
====================== SECTION_4 ( length=34, padding=0 ) ======================
1-4 section4Length = 34
5 numberOfSection = 4
6-7 NV = 0
8-9 productDefinitionTemplateNumber = 0 [Analysis or forecast at a horizontal level or in a horizontal layer at a point in time (grib2/tables/4/4.0.table) ]
10 parameterCategory = 0 [Temperature (grib2/tables/4/4.1.0.table) ]
11 parameterNumber = 0 [Temperature (K) (grib2/tables/4/4.2.0.0.table) ]
12 typeOfGeneratingProcess = 0 [Analysis (grib2/tables/4/4.3.table) ]
13 backgroundProcess = 0
14 generatingProcessIdentifier = 15
15-16 hoursAfterDataCutoff = 0
17 minutesAfterDataCutoff = 0
18 indicatorOfUnitOfTimeRange = 1 [Hour (grib2/tables/4/4.4.table) ]
19-22 forecastTime = 0
23 typeOfFirstFixedSurface = 100 [Isobaric surface (Pa) (grib2/tables/4/4.5.table) ]
24 scaleFactorOfFirstFixedSurface = 0
25-28 scaledValueOfFirstFixedSurface = 85000
29 typeOfSecondFixedSurface = 255 [Missing (grib2/tables/4/4.5.table) ]
30 scaleFactorOfSecondFixedSurface = MISSING
31-34 scaledValueOfSecondFixedSurface = MISSING
====================== SECTION_5 ( length=23, padding=0 ) ======================
1-4 section5Length = 23
5 numberOfSection = 5
6-9 numberOfValues = 1036800
10-11 dataRepresentationTemplateNumber = 40 [JPEG2000 Packing (grib2/tables/4/5.0.table) ]
12-15 referenceValue = 22676.8
16-17 binaryScaleFactor = 0
18-19 decimalScaleFactor = 2
20 bitsPerValue = 13
21 typeOfOriginalFieldValues = 0 [Floating point (grib2/tables/4/5.1.table) ]
22 typeOfCompressionUsed = 0 [Lossless (grib2/tables/4/5.40.table) ]
23 targetCompressionRatio = 255
====================== SECTION_6 ( length=6, padding=0 ) ======================
1-4 section6Length = 6
5 numberOfSection = 6
6 bitMapIndicator = 255 [A bit map does not apply to this product (grib2/tables/4/6.0.table) ]
====================== SECTION_7 ( length=624877, padding=0 ) ======================
1-4 section7Length = 624877
5 numberOfSection = 7
6-624877 codedValues = (1036800,624872) {
2.7052777344e+02, 2.7043777344e+02, 2.7054777344e+02, 2.7047777344e+02, 2.7043777344e+02, 2.7054777344e+02, 2.7046777344e+02, 2.7047777344e+02,
2.7048777344e+02, 2.7048777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7049777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7047777344e+02,
2.7048777344e+02, 2.7048777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7048777344e+02, 2.7046777344e+02,
2.7048777344e+02, 2.7049777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7047777344e+02,
2.7047777344e+02, 2.7048777344e+02, 2.7046777344e+02, 2.7048777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7048777344e+02,
2.7047777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7046777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7047777344e+02,
2.7047777344e+02, 2.7048777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7046777344e+02, 2.7048777344e+02, 2.7046777344e+02, 2.7047777344e+02,
2.7048777344e+02, 2.7046777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7046777344e+02, 2.7047777344e+02, 2.7048777344e+02, 2.7046777344e+02,
2.7047777344e+02, 2.7048777344e+02, 2.7046777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7046777344e+02, 2.7048777344e+02, 2.7047777344e+02,
2.7046777344e+02, 2.7047777344e+02, 2.7046777344e+02, 2.7048777344e+02, 2.7046777344e+02, 2.7046777344e+02, 2.7048777344e+02, 2.7045777344e+02,
2.7048777344e+02, 2.7046777344e+02, 2.7046777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7046777344e+02, 2.7048777344e+02, 2.7046777344e+02,
2.7046777344e+02, 2.7047777344e+02, 2.7047777344e+02, 2.7046777344e+02, 2.7047777344e+02, 2.7046777344e+02, 2.7046777344e+02, 2.7048777344e+02,
2.7045777344e+02, 2.7047777344e+02, 2.7046777344e+02, 2.7046777344e+02
... 1036700 more values
} # data_jpeg2000_packing codedValues
====================== SECTION_8 ( length=4, padding=0 ) ======================
1-4 7777 = 7777
从上面的输出结果可以看到，GRIB2消息包含9个部分（section 0~8）。下面结合样例文件中介绍每个section的具体内容。
